Glass Containers Can Cause Water To Flow More Like Ketchup On The Nanoscale

Georgia Tech associate professor Elisa Riedo poses with a glass water bottle and a plastic water bottle. While container materials don't significantly affect the rate at which water pours from bottles of this size, a new study shows that the properties of containers at the nanoscale dramatically affect the viscosity of water. Image Credit: Georgia Tech Photo: Rob Felt

Here’s a question that may not cross your mind when late for work – Is it quicker for me to drink from a glass or a plastic bottle?

Well, actually, it would make very little difference to your morning commute, but go down to

the nanoscale and the material a container is made of has a massive effect on the rate of flow of any water inside.

New research, sponsored by the Department of Energy's Office of Basic Sciences and the National Science Foundation, has shown that the viscosity of water can double when flowing through nanoscopic glass channels when compared to channels made of plastic.

Elisa Riedo, an associate professor in the School of Physics at the Georgia Institute of Technology, commented in a recent press release:

"At the nanoscale, viscosity is no longer constant, so these results help redefine our understanding of fluid flow at this scale”

This viscosity variation is affected by the hydrophobic properties of the container – i.e. how strongly it repels water. If water is more attracted to a certain material, moving the molecules becomes more difficult, hence leading to an increase in effective viscosity.

"We saw a clear one-to-one relationship between the degree to which the confining material was hydrophilic and the viscosity that we measured," - Elisa Riedo

This illustration shows how the different effective viscosity of water affects the force required to slide two surfaces separated by a thin layer of water when confined by a hydrophilic material or a hydrophobic material. Image Credit: Illustration courtesy of Elisa Riedo

Water confined on the nanoscale is prevalent in many diverse environments, from the human body to the rocks that comprise a mountain, so such variation in the way it flows at this scale could have a far reaching impact on future research.

This new research could also be of interest to designers of nanotechnology, such as that used in 3D printing and biomedical devices.

Similar studies will be undertaken to see if other liquids, such as oil, behave in the same manner.

"There is no reason why this should not be true for other liquids, which means that this could redefine the way that fluid dynamics is understood at the nanoscale," "Every technology and natural process that uses liquids confined at the nanoscale will be affected." - Elisa Riedo